Experiments with go "errgroup" package, multistream gzip and sparse files...
$ time tar czf /tmp/output-baseline.tgz /usr/lib/x86_64-linux-gnu/
real 1m20.265s
user 1m19.848s
sys 0m1.776s
$ time spack /tmp/output-cold.tgz /usr/lib/x86_64-linux-gnu/ # cold cache
real 0m24.339s
user 1m25.144s
sys 0m5.472s
$ time spack /tmp/output-hot.tgz /usr/lib/x86_64-linux-gnu/ # hot cache
real 0m2.824s
user 0m5.200s
sys 0m1.524s
$ du -bh /tmp/output*
483M /tmp/output-baseline.tgz
570M /tmp/output-cold.tgz
570M /tmp/output-hot.tgz
- we are using '-b' == "--apparent-size --block-size=1"
$ grep -c processor /proc/cpuinfo
4